1. Field of the Invention
The present invention relates to an object detection and tracking support system, a control method, and a program thereof. The invention particularly relates to an object detection and tracking support system that supports the detection of objects using detection waves generated from a transmitter, a control method for controlling the object detection and tracking support system, and a program for the object detection and tracking support system.
2. Description of Related Art
A sonar system, a radar system, and a lidar system detect and track objects using, respectively, sound waves, radio waves, and light waves. These kinds of system can increase the reliability of detection and provide a detection threshold by estimating the signal level from an object beforehand.
A detection signal level DL, in the case of a monostatic active sonar, can be expressed using the transmission level SL, the propagation loss TL, and the target strength TS, as DL=SL−2TL+TS, which is mentioned, for example, in ‘Marine Acoustics: Basics and Applications,’ Edition of Marine Acoustics Society of Japan, published by Seizando Shoten, May 2004 (Non-patent publication 1) p. 29. The transmission level SL is specified on the transmission side, and can easily be ascertained beforehand. The TS is different for each object, and can be ascertained by measuring it beforehand. In reality, however, it is often extremely difficult to measure the TS of the object in advance, and an estimate is therefore made using mathematical calculation and the like based on the supposed material, shape, and size of the object. The TL can be ascertained by actual measurement. While it is not feasible to measure the TL at every point. Propagation loss in the ocean is large due to spreading loss. The TL can be expressed in a mathematical formula as cylindrical spreading in shallow waters and spherical spreading in deep waters. By measuring the TL at a specific point, the TL at various places can be estimated based on a propagation loss equation. Incidentally, spherical spreading and cylindrical spreading are sometimes referred to as spherical dispersion and cylindrical dispersion. In this manner, it is possible to estimate the detection signal level at various points.
In a detecting and tracking device with a monostatic configuration, a transmitter and a receiver are provided at the same position. Therefore, propagation loss can simply be expressed as a function of the distance, irrespective of the direction.
In contrast, in a detecting and tracking device with a multistatic configuration, the transmitter and the receiver are provided at different positions. Consequently, the propagation distance from the transmitter differs depending on the direction of the object, even if the distance of the object from the receiver is identical. The propagation loss is therefore different in each direction. However, propagation loss that differs in each direction is expressed by a formula that includes both the distance and the direction viewed from the transmitter.
A region where the propagation loss becomes identical when viewed from the receiver is calculated from a numerical calculation that is complicated and requires high calculation capability, such as the FDTD shown in the Non-patent publication 1, p. 88. Thus, in a multistatic configuration, estimating the transmission level from an object viewed from the receiver is complicated and requires a considerable calculation load.